The present invention relates to a structure of a watch band and to a method of manufacturing the same.
Among various types of watch band, the type that enables watches to be worn most easily is the so-called expansion band. This is because, since the main body of a band of this type expands or contracts, one only has to expand the band and slip one's hand through it when putting the watch on one's wrist. In addition, the bands of other types involve such troublesome tasks as inserting the pin of a fastener into a hole in the band, in the case of a leather band, or engaging one end of the band with a fastener at the other end whenever the watch is to be put on. For these reasons, bands capable of expanding and contracting have conventionally been called expansion bands and used as watch bands.
A conventionally used expansion band is made of metal. Such a band has about 40 to 50 links linked together. A metal plate spring capable of deflection in the thickness direction of the band is inserted into each link, and spring stoppers, more specifically two spring stoppers per link, are inserted between the plate spring and the link from both sides of the link. Adjacent spring stoppers which are disposed on one of the respective sides thereof and inserted into the corresponding adjacent links are inserted into the other of the respective sides thereof between a rear plate and a plate spring within the rear plate. Since the width of a rear plate in the longitudinal direction of the band is equal to the width of a link, the links, the spring stoppers, and the rear plates are thus linked to each other in the successive order of a link, a spring stopper, a rear plate, a spring stopper, a link, a spring stopper, a rear plate, a spring stopper, and so on. When the band is expanded, the links and the rear plates are displaced in the longitudinal direction of the band, causing the spring stoppers to be inclined so that the sides of the spring stoppers at the center of the links cause deflection of the plate spring. Due to the resilience of the plate springs, the expanded band tends to contract again. The above description concerns a conventional expansion band.
A conventional expansion band has the above-mentioned structure. However, an expansion band with such a structure suffers from the following problems. The first problem is the large number of component parts. The entire structure of a band has 40 to 50 links, each with a plate spring received therein. In addition, two spring stoppers are provided for each link, and rear plates are required correspond in number to the links, each also requiring a plate spring received therein. Accordingly, if a band has 40 links, the additional component parts required for the entire structure of the band will be 40 rear plates, 80 (40+40=80) plate springs, and 80 (40.times.2=80) spring stoppers; the total number of these component parts is 240.
The second problem is encountered during assembly, and relates to the first problem. The assembly operation not only has to cope with the large number of component parts but also necessarily involves the steps of inserting a plate spring into each link and each rear plate, bending both ends of the plate springs in order to prevent disengagement of the plate springs, inserting spring stoppers into the respective gaps between the link and the plate spring and the rear plate and the plate spring, and finally caulking the rear plate in order to prevent disengagement of the spring stoppers. A band cannot be constructed until these steps have been completed with respect to all the links. The third problem is that the conventional structure of an expansion band fails to meet the recent demand for watches that are fashionable. Because these bands are made of metal, the variation of colors is limited. Although it is possible to vary the color by coating, some methods of coating may cause a problem relating to the expansion and contraction of the band, while others may suffer from the disadvantage of possible scaling off of the coating, thus failing to provide a solution to the problem. In addition, since manufacturing methods mainly comprise the work of bending metal, the work is necessarily restricted in a number of aspects, making it difficult for use of such a method to establish the desired structure of an expansion band using links and other component parts with unrestricted configuration.